The present invention relates to an antenna-mounting nut for securing an antenna body, which comprises an antenna element, to a vehicle.
Motor vehicle antennas, which are secured to a panel of a vehicle, are conventionally known. An example of a constitution of a motor vehicle antenna of this kind is shown in FIG. 6. This motor vehicle antenna, with the part that is mounted on the vehicle panel enlarged, is also shown in FIG. 7.
As shown in FIGS. 6 and 7, an antenna body 100 of an automobile antenna comprises an antenna cover 101 and an element portion 102 that is mounted on antenna cover 101, and a base 103 is secured to the lower end of antenna cover 101. A cylindrical protrusion 103a is formed on the lower face of this base 103 so as to protrude therefrom, as shown in FIG. 7, and antenna body 100 is secured by a mounting nut 106 threadedly engaging on this cylindrical protrusion 103a, such that a vehicle panel 110 is interposed therebetween. Here, the base portion of cylindrical protrusion 103a is formed as a rectangular protrusion, and a rectangular antenna-mounting hole is formed in vehicle panel 110, that enables this rectangular protrusion to be inserted therethrough.
Furthermore, an antenna top portion 102a of a diameter that is enlarged with respect to element portion 102 is provided at the upper end of element portion 102. The lower portion of element portion 102 is a molded portion 102b that is molded from a synthetic resin that is soft, such as a rubber. It is preferable for this molded portion 102b to be provided with an internal wave trap coil that is connected to the element.
Further, when the antenna is subjected to an external force, the soft molded portion 102b of the lower portion of element portion 102 prevents damage to element portion 102, by bending and absorbing the external force applied.
The electrical length from antenna top portion 102a of element portion 102 constituted in this way, to the base end portion of antenna body 100, is, for example, approximately one quarter of an FM radio band wavelength; and the electrical length from the base end portion to the lower end of the wave trap coil, is approximately one quarter of a mobile wireless telephone band wavelength. As a result, in addition to being resonant in a mobile wireless telephone band and the FM radio band, this motor vehicle antenna is capable of receiving radio waves in the AM radio band via the whole area of the antenna body 100.
Signals of this kind, which are transmitted and received by an element portion 102 are guided out by cables 107a, 107b that pass through cylindrical protrusion 103a. Cable 107a is a cable for a mobile wireless telephone and cable 107b is a cable for FM/AM radio.
When securing an antenna body 100 of this kind to a vehicle panel 110, the rectangular protrusion formed on base 103 is inserted into the rectangular antenna-mounting hole formed in vehicle panel 110, and mounting nut 106 is made to mate threadedly with cylindrical protrusion 103a that protrudes from this antenna-mounting hole, and mounting nut 106 is tightened. Antenna body 100 is thus secured such that vehicle panel 110 is interposed therebetween, as shown in FIG. 6.
Further, a base pad 104, which is constituted from a resin that is elastic, is mated with base 103, and an O-ring 105 is inserted so as to mate with cylindrical protrusion 103a. Cylindrical protrusion 103a is then inserted into the antenna-mounting hole. Through the action of this base pad 104 and O-ring 105, rainwater and so forth is prevented from penetrating vehicle panel 110.
Furthermore, mounting nut 106 is constituted from a washer portion of U-shaped cross-section 121 formed with triangular protuberances at the upper end thereof, and from a nut portion 120 that engages threadedly with cylindrical protrusion 103a. Further, when mounting nut 106 is fastened onto cylindrical protrusion 103a, triangular protuberances engage inside the rear face of vehicle panel 110 and base 103 is thus reliably grounded to vehicle panel 110.
Further, so that there is no damage to element portion 102, when collision is made with a rotating brush of a car wash, or the like, when washing the car in a car wash, or when contact is made with the ceiling of a garage or the like when the car is being parked therein, element portion 102 can be made to be removable from antenna cover 101.
The constitution of the above-mentioned mounting nut 106 that secures antenna body 100 to vehicle panel 110 is shown in detail in FIG. 8.
As shown in FIG. 8, a plurality of triangular protuberances 121a are formed at the upper end of washer portion of U-shaped cross-section 121, and washer portion 121 is caulked to nut portion 120 so as to be integral with nut portion 120. That is, a screw thread is formed in nut portion 120 that engages threadedly with cylindrical protrusion 103a of base 103, and a plurality of caulking pieces 120a are formed on the upper face of nut portion 120. Further, by placing washer portion 121 on the upper face of nut portion 120 and caulking caulking pieces 120a by means of a caulking tool, nut portion 120 and washer portion 121 are made integral. Here, since six caulking pieces 120a are provided and disposed in a hexagonal shape, washer portion 121 is capable of rotating with nut portion 120. For this reason, when nut portion 120 is fastened onto cylindrical protrusion 103a, triangular protuberances 121a of washer portion 121 rotate, causing stripping of the paint of vehicle panel 110, thus permitting a reliable grounding of base 103.
Problems are posed by the conventional motor vehicle antenna as described above, namely, that, when the vehicle panel where the antenna is mounted is deformed, the gap between mounting nut 106 and vehicle panel 110 changes fractionally, and there is a risk of the press-contacting force of mounting nut 106 weakening. When the press-contacting force of mounting nut 106 weakens in this way, the electrical connection between washer portion 121 and vehicle panel 110 becomes unstable, the grounding becomes unreliable, and a grating sound results.
Additionally, since stress is continually applied to base pad 104 and O-ring 105 by the fastening strength of mounting nut 106, there is a risk that, over the years, the elasticity of base pad 104 and O-ring 105 will weaken under this stress. Similarly here, there is the problem that the press-contacting force of mounting nut 106 weakens, the grounding becomes unreliable, and a grating sound results.
It is therefore an object of the present invention to provide an antenna-mounting nut that is capable of providing the antenna with a reliable grounding, even if the vehicle panel is deformed or the elasticity of the base pad or O-ring should weaken.
In order to resolve the above-mentioned object, a first antenna-mounting nut of the present invention engages threadedly, from the reverse side of the above-mentioned vehicle panel, with the protrusion, on the antenna body, that is inserted into the mounting hole formed in the vehicle panel, and comprises a washer portion, at whose upper end a plurality of serrate protuberances is formed that come into contact with the above-mentioned vehicle panel; a nut portion that engages threadedly with the above-mentioned protrusion; and a joint portion that integrally secures, via a wave washer, the above-mentioned washer portion and above-mentioned nut portion so that same do not rotate with respect to one another, and is characterized in that inclined faces of the above-mentioned serrate protuberances are formed facing in the direction in which the above-mentioned nut portion is fastened onto the above-mentioned protrusion.
Further, a second antenna-mounting nut of the present invention, that is capable of resolving the above-mentioned object, engages threadedly, from the reverse side of the above-mentioned vehicle panel, with the protrusion, on the antenna body, that is inserted into the mounting hole formed in the vehicle panel, and comprises a washer portion, at whose upper end a plurality of serrate protuberances is formed that come into contact with the above-mentioned vehicle panel and whose inclined faces are formed facing in the direction in which the above-mentioned nut portion is fastened onto the above-mentioned protrusion; and a nut portion that is secured to this washer portion so as to be prevented from turning, and that engages threadedly with the above-mentioned protrusion, and is characterized in that the above-mentioned washer portion is made elastic by being formed from an elastic material and by a plurality of slits being formed radially therein.
According to a first present invention of this kind, a wave washer is interposed between the washer portion and nut portion, meaning that even if the vehicle panel is deformed or the elasticity of the base pad or O-ring weakens, this change can be absorbed by the wave washer, and thus a reduction in the press-contacting force of the antenna-mounting nut can be prevented as far as possible. Further, the inclined faces of the serrate protuberances that are formed at the upper end of the washer portion are formed facing in the direction in which the nut portion is fastened onto the protrusion of the base; thus, during fastening, the antenna-mounting nut rotates smoothly, and, during loosening, since the serrate protuberances engage inside the vehicle panel, the antenna-mounting nut can be prevented from becoming loose.
Further, according to a second present invention, since the washer portion is made elastic by being formed from an elastic material and by a plurality of slits being formed radially therein, even if the vehicle panel is deformed or the elasticity of the base pad or O-ring weakens, this change can be absorbed by the elastic washer portion, and thus a reduction in the press-contacting force of the antenna-mounting nut can be prevented as far as possible. Further, because the inclined faces of the serrate protuberances formed at the upper end of the washer portion are formed facing in the direction in which the nut portion is fastened onto the base protrusion, during fastening, the antenna-mounting nut rotates smoothly, and, during loosening, since the serrate protuberances engage inside the vehicle panel, the antenna-mounting nut can be prevented from becoming loose.